This proposal describes a 5-year training program for the development of an academic career in Investigative Dermatology. The principle investigator has completed a residency in Dermatology from New York University and her MD/PhD from Stanford University. She has a strong track record of basic science research and will expand her scientific skills in human clinical translational methods, clinical trial design, and immuno-monitoring assays. She was previously mentored by the late Dr. Ralph Steinman, prior to his receipt of the 201 Nobel Prize in Medicine and with whom she initially formed this application and project. She will now be mentored closely by Dr. Michel Nussenzweig now- an outstanding HHMI investigator in adaptive immunity. Flt3L, a potent DC hematopoietin, expands CD8 cross-presenting dendritic cells (DC) in mice. Research will focus on the clinical development of Flt3L as an immune adjuvant to expand DC subset numbers in humans, testing its impact on immunity in humans and testing its preclinical efficacy in mice, when combined with protein-based DC targeted immunization. Flt3L has demonstrated safety in over 300 patients, but development of this agent was ceased due to commercialization issues. The FDA has recently lifted a clinical hold on Flt3L so studies to re-evaluate this agent can continue. The central hypothesis is that Flt3L will mobilize and expand cross-presenting DCs in humans, promoting superior T cell responses. In Provenge therapy (a DC therapeutic-vaccine targeted against prostate cancer), patients first undergo an expensive and complex leukapheresis procedure to obtain sufficient autologous cells to generate the DCs ex vivo to use for the vaccination. Using Flt3L offers an alternative approach to generate ample and more physiological DC precursors in vivo after simple injection, as a substitute for the current leukapheresis step. Thus these experiments may offer substantial improvement in such a DC-based anti-cancer strategy, and also develop an innovative approach to generating adjuvants, therapeutic DC-vaccines, and other combinatorial immunotherapy. The long-term goal is to investigate mechanisms to overcome tolerance and improve cutaneous immunity, focusing on biologic methods to potentiate particular DC in this application. The hypothesis is that Flt3L expands cross-presenting DC equivalents across species and can be used as an adjuvant. This hypothesis will be tested by pursuing 2 specific aims to (1) establish and profile CD8 equivalents in humans with Flt3L and compare human DC subset functions and assess alterations in de novo and recall immune responses after Flt3L treatment (2) assess whether Flt3L improved immunity when coupled to adjuvants for human use and DC targeted immunization in mice, that allow in vivo targeting without leukophoresis. It is innovative because the use of Flt3L to potentiate human cross-presenting DC with the goal of DC subset targeting is novel~ it uses advanced immunization methods to target DC with protein-based vaccines developed in the applicant's laboratory, and currently being tested in humans. The training program has been designed to ensure a command of dendritic cell biology as applied to immunotherapy and adjuvant design towards improved health and immunity. Prof. Michel Nussenzweig will mentor the principle investigator's scientific development. Dr. Nussenzweig is a key leader of the DC development, targeting, and leads the adaptive immune field. His work with Dr. Steinman has led to a new understanding of the control of tolerance and immunity. Dr. Nussenzweig has mentored numerous junior and senior faculty members. Training activities will be enhanced through focused instruction in advanced immunology and translational biology in a formal clinical translational program. A scientific advisory committee, composed of exceptional physician scientists, will provide scientific and career advice. The Laboratories of Cellular Physiology and Immunology and Molecular Immunology at Rockefeller University are the ideal setting for intensive training in bench and translational science skills required to address a complex area of clinical immunology. This environment will prepare the principle investigator for an academic career in investigative dermatology where she will address a role for immune adjuvants in improving cutaneous immunity and the prevention and treatment of skin cancers.